1. Field of the Invention
The present invention relates to fume collection systems for use with electric arc furnaces in steel production.
2. Description of the Prior Art
Electric arc furnaces are commonly used in the production of steel products, such as in melting scrap metal for the casting of steel products. During the production of the molten steel, fumes are typically produced and emitted from several locations, such as at the arc furnace roof, at the arc furnace back door, at an intake pipe such as a pebble lime intake pipe, and at the arc furnace spout. For environmental control, fumes have typically been collected from at least one furnace area or collection point, such as at the furnace roof. A duct has been provided from the collection point leading to a baghouse where the exhaust stream was filtered. An exhaust fan or fans are provided downstream of the baghouse to draw fumes from the furnace through the duct and through the filters at the bag house.
To improve environmental control, such systems have been supplemented by collecting fumes from additional arc furnace areas or collection points. However, to add additional collection points can overload the original system if the exhaust from the supplemental collection points is simply introduced into an existing duct system, since the exhaust fan capacity will have been designed for a lesser load. One solution is to add supplemental baghouses with their own exhaust fans to collect fumes from the additional collection points. Another solution is to introduce the additional fumes into the original duct system and to replace the original exhaust fan or fans with higher capacity devices. However, neither of these solutions is satisfactory. To add additional baghouses is expensive and may result in an inefficient use of plant space. To replace an exhaust fan with a more powerful exhaust fan can be inefficient and more costly to operate. Typically, it is not necessary to draw fumes from each collection point at the same rate on a continual basis since the quantity of fumes emitted varies over the production cycle. A fan powerful enough to draw fumes from several areas at certain times may have excess capacity at other times in the production cycle. To use a fan with excess capacity throughout the production cycle wastes energy and can therefore be unduly expensive to operate.